The writings of Nicolaus Copernicus were unavailable in English until the publication of this 1939 translation—presented here as an unabridged reproduction of the revised 1959 edition. The three-part collection consists of the "Commentariolus," Copernicus's sketch of his hypotheses for the heavenly motions; the "Narratio Prima," a popular introduction to Copernican theory; and the "Letter against Werner," Copernicus's refutation of the views of a contemporary.